Fix for char offset range component generation.
Fix for char offset range component generation.

This fixes generating a range component between a text node in an
element node and a text node with the same parent as the element node.

pmstss/readium-cfi-js,bibliolabs/readium-cfi-js,bibliolabs/readium-cfi-js,pmstss/readium-cfi-js,readium/readium-cfi-js